The present invention relates to an improved pressurized water nuclear reactor having an integral means for in-core spraying of a liquid coolant in case of a loss of coolant event, and a passive safety system incorporating an improved reactor vessel.
The nuclear power industry has been making efforts to provide for more safe operation of nuclear reactors. While some efforts have taken the form of adding more "active" safety features and then performing probability analyses to show that risks are very small, a portion of the public has remained unconvinced. In such active systems of the prior art, a large number of components such as pumps and fans which may be electrically powered, and optionally diesel powered in the event of electric failure, are provided. Thus, in a pipe break, termed a loss of coolant accident, water is provided to the primary circuit and then the reactor vessel by pumps. Additionally, motor-driven fans as well as pump-operated spray devices, are used to remove containment heat. The reactor decay heat and heat from containment is also transferred into an emergency cooling water system. These safety systems are all required to be redundant in order that failure of a component will not render the safety system ineffective. Thus, the active approach to nuclear plant safety results in plant designs of highly complex and costly design.
The need thus exists for a nuclear reactor, of the pressurized water reactor type, which is convincingly safe to one and all without significant increase in costs, which are already high. The most likely approach is thus a system which is of a "passive" nature, i.e. which requires little or no operator action but rather uses gravity or stored energy to perform its functions.
It is an object of the present invention to provide a pressurized water nuclear reactor which has a large volume of relatively cold supplementary pressurized water integral within the reactor vessel, which supplementary water is sprayed into the core of the reactor upon occurrence of a loss of coolant accident in the primary coolant circuit, without need for pumps or other active components.
It is another object of the present invention to provide a passive safety system incorporating the reactor of the present invention.